Start with getting your all your requirements laid out. After you have them, you can start dealing with your database design. You may want to see if your group has someone with some more design experience as it sounds like your database design may be rather complex. This probably isn’t the best database to be the first database that you design.
You should work on getting the bulk of the database designed before you write a line of C# code.
The more the database changes through out the process the more C# code you’ll need to rewrite.
I found one of the best ways to design a database is to lay out the requirements as stated above and to also draw it all out. When drawing all the requirements out you can then view all the relationships that you will have to make between the data. This also aids in running through the different scenarios that you may encounter with the data when importing and editing it. Keep the layout simple at first and then add onto it piece by piece. Look at the data that you will be importing and break it down into entities (ie. job candidates, resumes, applications, jobs etc) and draw them out on paper. After drawing out your entities you can then see how they relate to each other and draw out the relationships(ie. 1 candidate to many job applications submitted). There are some great books out there that will help with database design. Go through some of these books to get ideas on how they break down their data into manageable tables. My best advice is start out simple and then keep adding each complex piece to that. Hope this helps and hasn’t confused good. Have fun with your project.
In the MS SQL Server 2005 DBA certification book there is a story of a very similar real-life scenario with candidates job applications stored in database. It highly recommended using Full-Text indexing to handle querying applications, due to variations in the way that people describe themselves and their skills. It increased performance many-fold and reduced man-hours needed to mantain data . I would recommend reading up on Full-Text indexing if it is likely than the data will grow.